1. Field of the Invention
The present invention relates to an induced current position transducer for use in calipers, linear height gauges and linear scales, for example. More particularly, the present invention relates to an induced current position transducer capable of reducing harmful magnetic fluxes diffusing to the outside from the inside of the transducer to improve signal intensity.
2. Description of the Related Art
Electric calipers using an induced current position transducer have been developed and demonstrated in the art. In the induced current position transducer, a magnetic field generator generates a primary magnetic field, which couples to a first section in a coupling loop that consists of two loop sections. The first section generates an induced current in response to the primary magnetic field. A second section in the coupling loop generates a secondary magnetic field, corresponding to the induced current, which couples to a magnetic flux sensor. The magnetic flux sensor is arranged at a spatial period that corresponds to an array of coupling loops to provide a signal in accordance with a relative position of the coupling loop to the magnetic flux sensor.
The above signal processing technology may be applied to a measurement device. In this case, since the measurement device has restrictions from its characteristic on a structure and a structural material, it often employs a metal for the material. If the above technology is applied to a precise measurement under such the condition, it is required to maintain a magnetic flux intensity having a role of a signal with a possible minimal loss. Nevertheless, the primary and secondary magnetic fields diffuse along the members that construct the measurement device. As a result, an efficient magnetic coupling to the coupling loop can not be ensured and a sufficient signal intensity can not be obtained.
The present invention has been made in consideration of such the disadvantages and according has an object to provide a higher precise measurement technology by preventing harmful diffusion of magnetic fluxes and reducing a signal intensity variation in accordance with a distance (gap) variation between a coupling loop and a magnetic generator and magnetic flux sensor to improve a stability over the gap variation, and by forming a closed magnetic path between the coupling loop and the magnetic generator and magnetic flux sensor to improve the signal intensity.
The present invention is provided with an induced current position transducer, which comprises a first and a second members arranged opposite to each other and relatively movable along a measurement axis, the first and second members each having a first and a second magnetic flux regions formed normal to the measurement axis; a magnetic field generator for generating a first variable magnetic flux within the first magnetic flux region in response to a driving signal; a coupling loop having a first section located within the first magnetic flux region and a second section located within the second magnetic flux region, the first section generating an induced current in response to the first variable magnetic flux, and the second section generating a second variable magnetic flux corresponding to the induced current; and a magnetic flux sensor disposed within the second magnetic flux region for sensing the second variable magnetic flux, wherein any one of the magnetic field generator, the coupling loop and the magnetic flux sensor is located on one of the first and second members, and the remainder two on the other of the first and second members, and wherein a high permeable substance is disposed on at least a part of the first member, the second member and a gap between the first and second members to form a magnetic path for a flux permeating at least one of the magnetic field generator, the coupling loop and the magnetic flux sensor.
In a preferred embodiment of the present invention, the magnetic field generator and the magnetic flux sensor are located on one of the first and second members, and the coupling loop on the other of the first and second members.
In a second embodiment, the magnetic field generator and the coupling loop may be located on one of the first and second members, and the magnetic flux sensor on the other of the first and second members.
In a third embodiment, the coupling loop and the magnetic flux sensor may be located on one of the first and second members, and the magnetic field generator on the other of the first and second members.
Preferably, the magnetic flux sensor in the first and second embodiments and the magnetic field generator in the third embodiment have a plurality of regions alternating polarities along the measurement axis, which regions are formed in more detail in a periodic pattern with a certain wavelength along the measurement axis.
The high permeable substance may comprise a high permeable resin layered on, a magnetic material adhered on, or a magnetic material embedded in at least one of the first and second members.
The high permeable substance may also comprise a high permeable resin layered on the first member and/or the second member and patterned to cover the pattern of at least one of the magnetic field generator, the coupling loop and the magnetic flux sensor.
One of the first and second members is secured on a beam extending along the measurement axis, and the other of the first and second members is secured on a slider slidably mounted on the beam. The beam and slider may be composed of a magnetic material.
In the present invention, one of the first and second members is secured on a beam extending along the measurement axis, and the other of the first and second members is secured on a slider slidably mounted on the beam. Preferably, the beam is composed of a magnetic material, and in the slider at least one side opposite to the beam is composed of a non-magnetic material.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof.